Process of preparing yarn and knitting hose



United States Patent 3,417,174 PROCESS OF PREPARING YARN AND KNITTING HOSE Otto Jack Matray, Martinsville, Va., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Oct. 26, 1964, Ser. No. 406,566 2 Claims. (Cl. 26478) ABSTRACT OF THE DISCLOSURE A process for preparing womens hose by preparing the leg yarn from a first copolyamide which has been treated to reduce the shrinkage to the range of to 13% and preparing the welt yarn from a second copolyamide having the same polymer units as the first copolyamide but in different proportions and the second copolyamide having been treated to reduce the shrinkage to the range of 4 to 8% has been found to produce hose having the desired shrinkage and dyeing characteristics.

This invention relates to novel and useful hosiery and to an improvement in the production of hosiery.

Recently it has been found that ladies hose of improved fit, comfort and appearance result if certain copolymer compositions together with appropriate processing are used in the preparation of the hosiery yarn. These yarns are disclosed and claimed in copending application S.N. 275,162, filed Apr. 23, 1963 in the names of D. B. Cook and R. F. Lange now US. Patent 3,322,731.

A problem which occurs in the production of hose from copolymer yarns of this type is that welt yarn prepared from the same copolymer composition as the leg yarn is not altogether suitable due to the fact that the high shrinkage of the yarn, which is desirable in the leg yarn, makes it undesirable for welt construction. Welt yarns desirably have a shrinkage of about 4 to 8% in order to produce hosiery welts of the necessary size without knitting of undesirably large welts initially. Such shrinkage may be achieved from the copolymer yarns by severe heat treatment, but this is impractical with modern high-speed processing equipment. Welts prepared from 6-6 nylon have the required shrinkage characteristics, but dye to a different shade than the copolymer yarn and are therefore unsatisfactory.

It is an object of this invention to provide an improvement in the process for the production of hosiery from copolymer yarns. Another object is to provide a process for the production of copolymer leg and welt yarns which result in matched shrinkage and dyeing characteristics in the leg and Welt portions of the hose. Other objects will become apparent from the discussion and example to follow.

In accordance with the present invention, womens hose is provided knitted from hosiery denier yarn of a synthetic, liner copolycarbonamide, wherein recurring carbonamide linkages are an integral part of the polymer chain, at least 80 mol percentage of the said copolycarbonamide being of polyhexamethylene adipamide and polycaproamide copolymer units (i.e., 6-6/6 units), other copolymeric units, whenever present, being polyhexamethylene sebacamide (i.e., 6-10), the leg yarn of the said hose being a monofilament having a residual shrinkage in the greige of from about 10% to about 13% and the 6-6/6 copolymer units containing from about 10 to about mol percentage of 6 units, the welt yarn of the said hose being a multi-strand continuous filament yarn having a residual shrinkage in the greige of from about 4 to about 8% and the 6-6/ 6 copolymer units containing from about 6 to about 16 mol percentage of 6 units,

3,417,174 Patented Dec. 17, 1968 there being at least about 4 mol percentage less 6 units in the 6-6/ 6 copolymer of the welt yarn than in the leg yarn.

The above objects are accomplished in a process comprising (l) preparing the leg yarn by melt extruding and quenching a first copolyamide comprising a major proportion of one polymer unit and a minor proportion of a second polymer unit to form a filament, drawing and heat treating the filament to reduce the shrinkage to the range of 10 to 13% and (2) preparing the welt yarn by melt extruding and quenching a second copolyamide to form a plurality of filaments, converging the filaments to form a yarn, drawing and heat treating the yarn to reduce the shrinkage to the range of 4 to 8%, said second copolyamide comprising the Same major and minor polymer units as the first copolyamide, but the ratio of minor to major polymer units being substantially reduced relative to the ratio existing in said first copolyamide (3) knitting hose from the yarn so produced, and (4) dyeing the hose.

The preferred copolyamides for use in this invention are those prepared from hexamethylene diamine, adipic acid and epsilon-caprolactam, i.e., copolyamides of 6-6 and 6 nylon. Preferably, the leg yarn is prepared from a copolymer containing about 15% of 6 polymer units and about 85% of 6-6 polymer units and the welt yarn is prepared from copolymer containing about 10% to 6 polymer units and about 90% of 6-6 polymer units. However, desirable hose may be prepared from yarns extruded from copolymers containing from 5 to 20% of 6 polymer units, 90 to of 6-6 units, and up to 20% of 6-10 (hexamethylene sebacarnide) polymer units. The welt yarn should contain at least about 4% more of the 6-6 polymer units than the leg yarn to obtain the desired shrinkage level while maintaining a satisfactory dye match between the Welt and leg portions of the hose.

Yarn shrinkage values as reported herein are determined by boiling a measured length of yarn in water for 15 minutes, air drying the yarn and determining the reduction in length.

The expression relative viscosity as used herein refers to the ratio of the flow time in a viscometer of a polymer solution relative to the flow time of the solvent by itself. The measurement is made with 5.5 grams of polyamide in 50 ml. of 90% formic acid at 75 C.

EXAMPLE I After charging 68.6 lbs. of a 50% aqueous solution of a hexamethylene diamrnonium adipate (6-6 nylon salt solution) and 5.25 lbs. of epsilon caprolactam to an evaporator, 19.1 lbs. of Water are removed by heating at 12 p.s.i.g. pressure. The charge is then transferred to an autoclave, heated to a temperature of about 210 C. and brought to a pressure of 250 psi. At this point, 238.9 grams of a 20% aqueous slurry of titanium dioxide are added. The solution is then heated at 250 psi. until the temperature reaches 274 C. After the heating period, pressure is reduced over a period of 90 minutes to atmospheric and the temperature is increased to 279 C. The polymer is then held 60 minutes at this temperature after which it is extruded under 50-70 p.s.i. nitrogen in the form of a ribbon which is quenched on a water-cooled casting wheel and cut into A" flake in the conventional manner. The polymer flake contains of 6-6 polymer units and 15% of 6 polymer units and has a relative viscosity of 44.

The polymer is melted on a grid, extruded to form monofil for hosiery leg yarn, air quenched and wound into packages at 461 y.p.m. in the conventional manner.

The yarn is cold drawn to a ratio of 4.35 on a drawtwister. The yarn is subjected to a hot annealing and relaxation treatment on the drawtwister by carrying the yarn in a number of passes around a stepped roller, the

larger diameter portion of which serves as the draw roller while the smaller diameter portion permits the yarn to relax. The yarn is given 4 passes around the larger portion of the roller and an associated separator roller followed by 5 passes around the smaller diameter portion of the roller and the separator roller. A heating element is placed between the step roller and the separator roller so that the yarn contacts either side of the heating element for a distance of 3 inches on each pass around the step roller. The temperature of the heating element is 170 C. By this means the yarn is given a hot annealing treatment at constant length around the larger diameter portion of the step roller and the separator roller and is permitted to retract about 13% as it proceeds around the smaller diameter portion of the step roller. After the heat treatment the yarn is wound into a package in the conventional manner. The final denier of the monofil is 15. The shrinkage of the monofil in boiling water is -13%.

Welt yarn is prepared following the general procedure given above with the following exceptions. The copolymer is prepared to contain 90% 66 units and 10% 6 units and has a relative viscosity of 38. The copolymer is extruded to form a 10 filament yarn having a final drawn denier of 50. The draw ratio is 4.29. The temperature of the heating element is 215 C. The yarn is given 10 wraps around an annealing roller with its associated separator roller and heating element. The shrinkage of the final yarn is 67%.

The leg and welt yarns prepared as above are knitted into hose on a single feed Scott & Williams seamless knitting machine (400 needles) to yield preboarded course-counts of about courses per inch in the knee when measured on the table top. The hose are preboarded using a board having a width of 6 inches at the knee, 4% inches at the calf and 2 inches at the ankle. The hose, pulled down loosely on the board, are exposed to '6 psi. steam for 3 minutes.

A number of hose, prepared as described above, are d'yed according to standard conditions except for a lower dye bath temperature, 65.6 C. and then post-boarded at 82.2 C. for one minute. The hose welts behave satisfactorily with respect to shrinkage and a satisfactory dye match between the welt and leg portions of the hose is obtained. By comparison, when a standard 66 nylon hosiery yarn is used in the welt, a satisfactory dye match between the welt and leg portions is not obtained. When an 85/15, 66/6 copolymer composition is used in the welt yarn under identical processing conditions, the shrinkage of the welt yarn is too high to meet finished welt stretch requirements and larger welts (bigger loops) must be knitted. These larger welts give unacceptable knitting performance and appearance.

When the hose of this invention are wear-tested, they are found to give improved fit, comfort and appearance relative to commercial 66 nylon hose.

This invention provides a solution to the problem of producing copolymer hosiery welt and leg yarns which provide a satisfactory match with respect to shrinkage and dye depth in the welt and leg portions of the hose. Although the ditferences involved may appear small to the uninitiated, they are critical with regard to commercial sale of yarn for hosiery production. The invention is particularly useful in the production of welt and leg yarns from the 66/ 6 copolymer compositions set forth above, but obviously may be used to advantage where copolymer compositions are used for hosiery yarn production.

The welt yarn should be prepared from copolymer containing at least about 4% more of the major polymer unit than the leg yarn. Usually, no more than about 10% difference in this respect will be required and for optimum results a 47% difference is usually desirable.

Many equivalent modifications of the present invention will be apparent to those skilled in the art from a reading of the above without a departure from the inventive concepts.

What is claimed is:

1. A process for preparing womens hose comprising (1) preparing the leg yarn by melt extruding and quenching a first copolyamide comprising a major proportion of one polymer and a minor proportion of a second polymer unit to form a filament, drawing and heating treating the filament to reduce the shrinkage to the range of 10 to 13% and (2) preparing the welt yarn by melt extruding and quenching a second copolyamide to form a plurality of filaments, converging the filaments to form a yarn, drawing and heat treating the yarn to reduce the shrinkage to the range of 4 to 8%, said second copolyamide comprising the same major and minor polymer units as the first copolyamide, but the ratio of minor to major polymer units being substantially reduced relative to the ratio existing in said first copolyamide, and wherein said first copolyamide comprises about 15% of 6 polymer units and about of 66 polymer units and said second copolyamide comprises about 10% of 6 polymer units and about of 66 polymer units (3) knitting hose from the yarn so produced.

2. Claim 1 wherein said hose are knitting.

dyed following said References Cited UNITED STATES PATENTS 3,322,731 5/1967 Cook et al. 26078 JULIUS FROME, Primary Examiner. A. KOECKERT, Assistant Examiner.

US. Cl. X.R. 264l03; 66l78, 202 

